1. Field of the Invention
The present invention relates to a motor-driven compressor formed integrally with a compression portion and a motor for compressing refrigerant, and, more specifically, relates to a motor-driven compressor that is suitable for use in an air conditioner for vehicles.
2. Description of Prior Art
A motor-driven compressor is driven by a power supply, for example, an external power source such as a battery. A known motor-driven compressor is constructed as depicted in FIG. 5. In FIG. 5, motor-driven compressor 50 includes discharge housing 51, intermediate housing 52, and suction housing 53. Fixed scroll member 60 and orbital scroll member 70 are provided in discharge housing 51. Rotation prevention mechanism 68 prevents the rotation of orbital scroll member 70. These members and the mechanism constitute a refrigerant compression portion 75, that is formed as a scroll type compressor mechanism.
Drive shaft 55 is disposed in intermediate housing 52 and suction housing 53. Rotor 83 is provided around drive shaft 55, and stator 81 equipped with coil 82 is provided around rotor 83.Stator 81 is fixed on the inner surfaces of intermediate housing 52 and suction housing 53. Stator 81, coil 82 and rotor 83 form a motor 80. Refrigerant suction port 76 is provided at the end portion of suction housing 53.
Drive shaft 55 has a small diameter portion 55a at one end portion, and a large diameter portion 55b at the other end portion. Small diameter portion 55a is rotatably supported by suction housing 53 via bearing 56. Large diameter portion 55b is rotatably supported by intermediate housing 52 via bearing 57. Eccentric pin 55c projects from the end surface of large diameter portion 55b in a direction along the axis of drive shaft 55. Eccentric pin 55c is inserted into eccentric bush 58, which is rotatably supported on the back surface side of orbital scroll member 70 via bearing 59.
In motor-driven compressor 50, drive shaft 55 is rotated by the rotation of motor 80. Orbital scroll member 70 is driven orbitally via the operation of the mechanism formed by eccentric pin 55c and eccentric bush 58. Refrigerant sucked through suction port 76 is introduced into fluid pockets, that are formed between spiral elements 62 and 72 of fixed scroll member 60 and orbital scroll member 70, from suction chamber 69 through the interior of suction housing 53 and intermediate housing 52. The refrigerant introduced into the fluid pockets is compressed by operation of the scroll type compressor. The compressed refrigerant is discharged from discharge port 67 to the outside through discharge hole 65 and discharge chamber 66.
In such a motor-driven compressor 50, motor-driven compressor 50 is separated from a drive circuit (not shown) for controlling the driving of motor 80. Motor 80 of motor-driven compressor 50 and the drive circuit are connected by lead wires (not shown). Therefore, the size of the system including motor-driven compressor 50 and the drive circuit may increase. Further, the system requires relatively long lead wires. Moreover, assembly of the system may take a long time.
Moreover, the drive circuit generally includes an inverter for converting power supplied from a power source into a suitable current for motor 80. Such an inverter generally comprises a plurality of switching elements. The switching elements may radiate a large amount of heat caused by, for example, electrical loss in the switching elements. Therefore, an air-cooled or water-cooled type inverter has been used for a known motor-driven compressor. In the air-cooled type inverter, a radiator or a fan is required. In the water-cooled type inverter, a water cooling radiator and water circulating pipes are required. Such equipment causes an increase in the cost of manufacturing the system.
Further, because generally a high-frequency, chopped current from the inverter is supplied to motor 80, electromagnetic waves are radiated from the long wires connecting motor 80 and the drive circuit. This may cause electromagnetic noise in a radio or other electronic equipment mounted on the vehicle.